Management and Evaluation of Large Scale Water System for Sustainable Agriculture Development and for Envilonment Maintenance.

流域内广泛分布的大水系的管理以流域回流再利用机制为特征。在本研究中，(1)分析了具有不同条件的几个水系统的用水模式，(2)从系统用水模式的角度阐明了水质的变化过程。在不同条件下农村环境维护的研究成果中，提出了几种合理的水管理技术，并对鹿儿川流域(溪流区)、鹿浦区(封闭水盆和水稻区)、品野川流域(低洼水稻区)、石家河流域(宽水稻区)和仙台川盆地(狭窄倾斜区)进行了实地调查和实验分析。结合各区域的水质状况，分析了区域水管理的特点，指出了影响区域水管理的因素。特别是理论和实验分析，阐明了(1)系统中水的循环速度(系统中水的回用率)与(2)水质指标(如溶解氧、总氮、总磷等)之间的动态关系，并以原创论文的形式发表在多个期刊上。

Managements of large water system widely spreading in river basin is characterized by the reuse mechanism of return flow in the basin. The effective water use is performed using the mechanism.In this research, (1) water use patterns were analyzed for several water systems having various conditions, and (2) the changing process of water qualities were clarified concerning water use patterns in the systems. Several technics on reasonable water management were proposed as the results of the research for keeping environmental maintenance in rural areas having various conditions.Field surveyings and experimental analyzings were carried out for several areas i. e., The Kasagawa Basin (creek area), The Kasumigaura District (closed water basin and paddy area), The Shinanogawa Basin (low lying paddy area), The Ishikarigawa Basin (wide paddy area) and The Sendaigawa Basin (narrow & inclined area). The characteristics of water management were examined and the factors affecting the water managements were pointed out with considering the water qualities for each area. Particularly, theoretical and experimental analyzes for clarifying the dynamic relationships between (1) cyclic velosity of water in the system (the reuse ratio of water in the system) and (2) water quality indexes such as dissolved oxygen, total nitrogen, total phosphate and so on.The obtained results concerning this research were published as original papers in several journals.